1. Field of the Invention
The invention relates to a chromakey method for inserting a background picture signal into key color-characterized key regions of a foreground picture signal, in which method fading operations are performed between the picture signals in proportional zones in dependence upon a control signal, while intermediate colors occurring in the proportional zones in the foreground signal are transformed into new intermediate colors which constitute a transition from the color of the foreground picture signal to that of the background signal.
2. Description of the Related Art
Such a chromakey method, in which there is a soft fading between the foreground picture signal and the background picture signal, and conversely, in a proportional zone, is proposed in the non-prepublished prior German Patent Application DE-A 41 42 650. At the transition of the actual picture contents and its colors to the key region and the color in that region, transition colors occur in the foreground picture signal, which transition colors become disturbingly manifest when there is an abrupt change-over from the foreground signal to the background signal. In accordance with the above-mentioned prior Patent Application, there should be a soft fading between the foreground picture signal and the background picture signal, while these transition colors should be transformed. In the transformation of the transition colors, an orientation with respect to the colors of the background picture signal-is realized so that the transition colors, no longer vary between the color of the foreground picture signal and the key color, but between the color of the foreground picture signal and the color of the background picture signal.
However, the problem of this method is that this proportional zone can only be fixed jointly for all foreground colors. Moreover, these colors may vary through several pictures/sub-pictures so that under circumstances, a proportional zone once fixed is no longer optimal. A correction could be performed by manually correcting the control signal which controls the fading in the proportional zone.